World Record Set for Optical High-Speed Signals

A world record in the measurement of optical high-speed signals was announced at the Europea Conference on Optical Communication, held last month in Berlin. Researchers with the Department of Microtechnology and Nanoscience at Chalmers University of Technology, Gothenburg, Sweden, and spinoff company PicoSolve Inc., said they have "used the best optics capability and combined it with the best electronics capability to circumvent bandwidth bottlenecks."

PicoSolve makes all-optical sampling oscilloscopes for high-speed testing to industries involved in the production of fiber communication devices, components, systems, sub-systems, and to R&D laboratories.

Peter Anrekson, a coauthor of the paper based on the research ("100 GSample/s optical real-time sampling system with Nyquist-limited bandwidth," Proc. European Conference on Optical Communication, Berlin, Germany, September 2007, post-deadline paper PDP1.1), said the technology could be commercialized in the next couple of years.

"There is now an emerging need for better test and measurement tools to allow for detailed analysis of next-generation telecommunications systems," Andrekson said. "Next-generation optical communication systems are expected to occupy 40-GHz bandwidth per channel and incorporate advanced modulation formats."

PicoSolve said its Chalmers high-speed optical oscilloscope is an invaluable tool to build and analyze such systems, since this cannot be managed by current methods.

"Today's systems for acquiring high-speed optical signals have a resolution limited by the bandwidth of the electronics after detection of the optical signal," the company said in a statement. "This bandwidth is currently 15 GHz or less for real-time sampling systems, i.e., systems that can also capture the true signal if it only occurs as a single event. Another limitation is the Nyquist sampling theorem, which postulates that the highest accurately represented signal frequency is half the sampling rate, e.g., 10 GHz at a sampling rate of 20 samples per second. This limitation, however, has not been of practical interest for high-speed signals -- until now."

Researchers at Chalmers separated the sampling of the high-speed optical signals into two parts: First, to sample the signal with an optical sampling technique, which has very high bandwidth, and to parallelize the result into four outputs.

In the second part, the four outputs were detected and sampled using a commercially available real-time sampling system (4 x 25 GSa/s). This results in a 100GSa/s sampling system with a "Nyquist-limited" bandwidth of 50 GHz -- three times larger than what's available today. In addition, the system memory depth is the same as for conventional systems, which means the concept can be of significant practical use in the future, the researchers said.

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